CASTEL GANDOLFO, Italy – Pope Benedict XVI said Sunday that he is "deeply sorry" his remarks on Islam and violence offended Muslims, but the unusual expression of papal regret drew a mixed reaction from Islamic leaders as the Vatican worried about a backlash of violence.

Some Muslim leaders accepted the statement. Others said it wasn't enough, but urged Muslims to avoid violence after attacks on churches in Palestinian areas and the slaying of a nun in Somalia.

Benedict said he regretted causing offense with his speech last week in Germany, particularly his quoting of a medieval text that characterized some of the teachings of Islam 's founder as "evil and inhuman" and referred to spreading Islam "by the sword."

"I hope that this serves to appease hearts and to clarify the true meaning of my address, which in its totality was and is an invitation to frank and sincere dialogue, with great mutual respect," the pope said during his weekly Sunday appearance before pilgrims.

It was an unusual step for a leader of the Roman Catholic Church. Benedict's predecessor, Pope John Paul II, issued a number of apologies during his papacy, but they dealt with abuses and other missteps by the church in the past rather than errors on his own part.

Vatican officials had earlier sought to placate spreading Muslim anger by saying Benedict held Islam in high esteem and stressed that the central thrust of his speech was to condemn the use of any religious motivation for violence, whatever the religion.

While Benedict expressed regret his speech caused hurt, he did not retract what he said or say he was sorry he uttered what proved to be explosive words.

Anger was still intense in Muslim lands.

Two churches were set on fire in the West Bank, raising to at least seven the number of church attacks in Palestinian areas over the weekend blamed on outrage sparked by the speech.

There was also concern that the furor was behind the shooting death of an Italian missionary nun at the hospital where she worked for years in the Horn of Africa nation of Somalia. The killing came just hours after a Somali cleric condemned the pope's speech.

"Let's hope that it will be an isolated fact," the Rev. Federico Lombardi, Vatican spokesman, was quoted as saying by the Italian news agency ANSA.

He said the Vatican was "following with concern the consequences of this wave of hate, hoping that it does not lead to grave consequences for the church in the world."

Police across Italy were ordered to step up security out of concern that the anger could cause Roman Catholic sites to become terrorist targets. Police outside the pope's summer palace confiscated metal-tipped umbrellas and bottles of liquids from faithful.

Benedict's expression of sorrow for the offense he caused satisfied some Islamic leaders.

The head of the Muslim Brotherhood in Egypt, a banned group but still the largest Islamic movement in that country, said the outrage was justified but predicted it would subside quickly.

Germany's Central Council of Muslims welcomed the pope's comments Sunday as "the most important step to calm the protest" and urged the Vatican to seek discussion with Muslim representatives to avoid lasting damage.

But others were still demanding an apology for the words, including in Turkey, where questions have been raised about whether Benedict should go ahead with a visit scheduled for November as the first trip of his papacy to a Muslim nation.

"It is very saddening. The Islamic world is expecting an explanation from the pope himself," Turkish State Minister Mehmet Aydin told reporters in Istanbul. "You either have to say this 'I'm sorry' in a proper way or not say it at all. Are you sorry for saying such a thing or because of its consequences?"

Turkish Education Minister Huseyin Celik voiced similar concern. "It is different to be sorry and to apologize," he said.

Malaysian Foreign Minister Syed Hamid Albar told Malaysian journalists late Sunday that the pontiff must offer a full apology and retract what he said.

"Muslims have all this while felt oppressed, and the statement by the pope saying he is sorry about the angry reaction is inadequate to calm the anger, more so because he is the highest leader of the Vatican," Syed Hamid was quoted as saying by the Bernama news agency at the end of a meeting of the Nonaligned Movement in Havana, Cuba.

Mohammad al-Nujemi, a professor at the Institute of Judicial and Islamic Studies in Riyadh, Saudi Arabia, expressed dismay at what he called Benedict "evading apology."

In Damascus, Syria, lawmaker Mohammad Habash said the pope offered a "clarification and not (an) apology." But Habash also called for "calm and dialogue."

Hundreds of Iranians demonstrated against the pope in cities across Iran. In Qom, the religious capital of Iran's 70 million Shiite Muslims, hard-line cleric Ahmad Khatami said the pope and President Bush were "united in order to repeat the Crusades."

The uproar is one of the biggest crises involving the Vatican in decades, and the Holy See has moved quickly in trying to defuse anger.

On Sunday, in an unusual step, the Vatican's press office rushed out translations in English and French of the pope's remarks. Typically, the Vatican doesn't translate the pope's Sunday remarks, which are delivered in Italian.

Both sides have much to gain by good relations. The Vatican and Muslims have shared stands in opposition of abortion. The Holy See, under Benedict's predecessor, John Paul II, vigorously lobbied against the Iraq war, and Benedict made numerous appeals to Israel to use restraint in its recent military campaign against Hezbollah guerrillas in Lebanon.

Russian President Vladimir Putin earlier urged world religious leaders to show "responsibility and restraint" to avoid what he called "extremes" in relations between faiths.